The present invention, in some embodiments thereof, relates to material science in general, and, more particularly, to sequence variants of Stable Protein 1 (SP1), to uses thereof, and to new and improved composite materials based on these SP1 variants.
Stable protein 1 (SP1) is a homo-oligomeric protein isolated from aspen (Populus tremula aspen) plants which forms a ring-shape dodecameric particle with a central cavity. The oligomeric form of SP1 is an exceptionally stable structure that is resistant to proteases, such as trypsin, V8, and proteinase K, high temperatures, organic solvents, and high levels of ionic detergent.
WO 2002/070647, WO 2004/022697, U.S. Patent Application Nos. 20030092624, 20050074763 and 20060172298 and U.S. Pat. No. 7,253,341, teach novel denaturant-stable, protease resistant, homo-oligomeric stable protein (SP) variants, having chaperone-like activity as well as methods of production and purification of these novel SPs. These documents also provide nucleic acids encoding SPs, methods of isolating nucleic acids encoding SPs, antibodies recognizing SPs, and the use of these SPs for stabilizing, refolding, repairing, preventing aggregation and de-aggregating macromolecules such as proteins, fusion proteins including SPs, nucleic acid constructs encoding the fusion proteins and their uses in a variety of methods and applications.
WO 2007/007325 [PCT/IL2006/000795] teaches SP1 and modified SP1 variant polypeptides, capable of forming reversible and covalent molecular associations with substances, compositions-of-matter comprising same, and various uses thereof.
The use of proteins in the production of composite materials is of growing interest, for example, in the fields of nano-biotechnology and engineering, and biomaterials applications. However, while the naturally occurring variety of protein structure and function is impressive, biomaterial fabrication is inherently limited by the availability, inflexibility, low stability and non-specific binding of the native protein pool.
Proteins accumulate at interfaces, a property that can be both a practical asset and a drawback. Most proteins are large amphiphatic molecules, intrinsically surface-active, but whose interaction with surfaces is difficult to gauge. Prediction and determination of the parameters governing protein adsorption and desorption behavior is complicated by the interplay of intermolecular forces, such as Coulombic forces, Van der Waals forces, Lewis acid-base forces, entropically-based effects such as hydrophobic interactions, conformational entropy and restricted mobility, and intramolecular forces within the protein molecules affecting protein conformation.
Engineered proteins can allow a degree of synthetic flexibility, by providing specific binding domains, however, while the behavior of single peptide functional domains may be predicted to moderate accuracy, prediction of the behavior of engineered proteins comprising multiple domains is much more challenging due to higher order organization, increased size and complex topology. Likewise, although techniques such as phage display have provided a wealth of useful peptides that bind inorganic molecules, the mechanisms governing binding specificity and target recognition are poorly understood.
Carbon Nanotube Reinforced Composite Materials
Carbon nanotubes are nano-scale hollow cylinders of graphite carbon atoms. They provide the highest Young's modulus (stiffness), highest thermal conductivity, highest electrical conductivity, and highest current density of any known material, while having a low density. Carbon nanotubes come in two forms, as single-walled carbon nanotubes and multiwalled carbon nanotubes. Singlewalled carbon nanotubes tend to be stronger, more flexible, more transparent and better electrical conductors and are more transparent, but due to high production costs, multi-walled carbon nanotubes are more widely used in composite materials.
When carbon nanotubes are added to a matrix material, the composite will take on some of the carbon nanotubes' properties, due to the rule of mixtures. However, the theoretical property values of carbon nanotubes composites are presently not attained due to the inability to efficiently produce fully integrated composites.
Due to insufficient bonding across the interface of the nanotube and matrix material, before carbon nanotubes can be used in a broad range of applications, methods for manipulating the positioning, orientation, anchoring, grafting and binding of the carbon nanotubes to the matrix are presently required, particularly where such anchoring, grafting and binding is done without metal.
Thus, there is a widely recognized need for, and it would be highly advantageous to have SP1 variants capable of forming molecular complexes with carbon nanotubes useful for effective production of highly specific composite materials such as polymers and polymeric fabrics with integrated carbon nanotubes.
Tires:
Rubber is commonly compounded with carbon black to improve its tensile strength and wear resistance. The rubber composition of a tire tread is often compounded with silica, as a reinforcing agent in place of the carbon black, to improve rolling resistance and running performance (e.g. wet properties) of the tire. However, in silica compounded tires, due to the poor conductivity of the compounded rubber, static electricity charged in vehicles results in problematic and poorly controlled discharge phenomenon, resulting in radio noise, adverse influence to electronic circuit parts, generation of short-circuit, and the like.
Poor conductivity of rubber tires and tire tread is also an obstacle to efforts to obtain detailed, real time information regarding parameters of physical properties and function of the tire, especially during use. Thermal conductivity, a critical parameter to tire performance and safety, is also limited by the poorly conductive rubber compounds and fillers commonly used in tire manufacture.
Methods of enhancing electrical and thermal conductivity of tires have been proposed. US Patent Application 2010078103, to Nakamura, discloses a pneumatic tire comprising a tire carcass ply from conductive rubber material formed so as to create a continuous conductive path for discharge of static buildup to the road surface. Carbon-black reinforced rubber is envisioned as the conductive rubber material.
U.S. Pat. No. 7,528,186 to Halasa, et al, discloses a pneumatic tire with enhanced conductivity comprising a tire tread from conductive rubber material incorporating carbon black and an ionically conductive compound, such as tetrachloroaluminate; tetrafluoroborate; thiocyanate; thiosalicylate, phosphonium, imidazolium, pyrrolidinium and pyridinium, and the like.
U.S. Pat. No. 7,337,815 to Spadone discloses a pneumatic tire having tread fashioned from rubber compounds of varying carbon black contents, in order to improve thermal conductivity and heat transfer to the road during use.
U.S. Pat. No. 7,318,464 to Hahn et al discloses a pneumatic tire having an electrically conductive element adhesively bonded to the inner surface of the tire cavity, such as a wire, for example, for communicating information on tire status.
U.S. Pat. No. 7,284,583 to Dheur et al discloses a pneumatic tire comprising an electrically conductive cord, fashioned from carbon fiber, metal filament or a combination thereof, extending from the bead to the tread, in order to provide a path of least electrical resistance from tire mount to road-contact surface.
U.S. Pat. No. 7,131,474 to Sandstrom discloses a pneumatic tire with a carbon-black-rich tread zone providing an electrically conductive path from the tire throughout the tread to the road.
U.S. Pat. No. 7,581,439 to Rensel, et al. discloses a pneumatic tire incorporating micro-scale sensors or a sensor layer, which can be fashioned from a conductive polymer, for gathering and transmitting a wireless signal containing information on the tire condition and performance.
U.S. Patent Application 0070028958 to Retti discloses an electrical energy generating tire with a conductive strip, for example, a conductive polymer, and an energy generating component (such as a piezo-ceramic or thermal-harvesting material) incorporated into the tread and/or sidewall of the tire.
U.S. Patent Application 0090314404 to Rodgers et al discloses a tire having at least one active material element capable of modifying the performance characteristics of the tire (e.g. rolling resistance). Active materials are defined as compositions that can alter stiffness, modulus, shape and/or dimensions in response to an activation signal, such as shape memory alloys, electroactive polymers, piezo-electric materials, electrorheological elastomers and the like, suitable for embedding in a tire construction.
US Patent Application 20060061011 to Kikuchi et al discloses a pneumatic or solid tire fashioned from a composite material incorporating oriented carbon nanotubes, for enhanced thermal conductivity and heat dissipation from the tires.
However, methods for the production and use in tire manufacture of such composite materials incorporating elements having enhanced conductivity such as carbon nanotubes suffer from the shortcomings mentioned hereinabove (difficulties in integration, positioning, orientation, anchoring, grafting and binding of the carbon nanotubes to the matrix). Thus, it would be advantageous to have improved composite polymers and polymeric fabrics comprising integrated carbon nanotubes for enhancing electric and thermal conductivity of tires.